There are currently a number of known workheads used in forestry which are each specifically designed for one or more particular functions involved in timber processing. For example, there are certain workheads which are adapted for use in the felling of trees, others for removing the bark or for removing the limbs from felled trees, others for the "bucking" or cutting of felled trees to length, and yet others for the loading or carriage of processed logs into storage regions or onto transport vehicles. It is also often necessary to design such workheads so that they are specifically capable of use with either hardwood or softwood, or particular tree species.
An example of a prior art timber processing device specifically adapted for tree felling is provided by International Application No. PCT/SE93/00601, published on Jan. 12, 1995 in the name of Widegren. The device according to Widegren includes a pair of shearing elements together with a sawing device, so as to effect tree felling either by sawing or shearing. Another dedicated cutting and sawing unit is exemplified by International Application No. PCT/SE91/00606, published on Apr. 2, 1992 in the name of Jansson. The unit according to Jansson includes a saw rotatably mounted on a motor stand and knives which project from a hub part of the saw. The knives co-act with a toothed device on the motor stand, such as to obtain a cutting action in addition to a sawing action.
Devices intended for dedicated tree delimbing are exemplified by the teachings of Australian Patent Application No. 76409/91, published on Nov. 14, 1991 and identifying Wingate-Hill et al. as inventors, Australian Patent Application No. 29636/92 published on Nov. 26, 1992 in the name of Milbourn, and Australian Patent No. 618,679 granted Jan. 2, 1992 in the name of Milbourn. The Wingate-Hill et al. device comprises a milling head having helical cutters, the milling head being mounted on support means such that the axis of rotation of the head is substantially parallel to the longitudinal axis of the trunk or log being delimbed. The first Milbourn device mentioned above consists of a workhead housing having a circular cutter wheel mounted thereon to rotate about a vertical axis. A chain saw is mounted by a swivel device on the housing and above the wheel. The second-mentioned Milbourn device consists of a workhead mounted on an articulated boom that can move vertically along a tree to trim the branches thereof.
Some known timber processing workheads provide a debarking roller assembly which engages the trunk of a felled tree and is configured so that when the rollers are activated, the trunk is drawn between the roller assembly. By their compressive action against the trunk, the rollers of the assembly cause the tree bark to loosen or separate from the truck, thereby at least partially debarking the trunk of the tree. This technique of timber debarking is known to those skilled in the art as compression debarking. Because of the nature or construction of compression debarking rollers currently in use, the debarking capability of some such rollers is limited. This deficiency may require supplementing the debarking action of the rollers, for instance by providing fixed or rotating knife edges to cut through bark which becomes loosened from the tree trunk, but which is not entirely removed by the rollers, or by arranging as many as six compression debarking rollers in an apparatus to ensure adequate circumferential coverage of a tree trunk drawn therebetween.
An example of a prior art debarking apparatus is found in U.S. Pat. No. 4,875,511, issued on Oct. 24, 1989 in the names of Wingate-Hill et al. This patent teaches the use of a plurality of pairs of concave rollers which are mounted in a spaced apart configuration along the linear passage of the log through the apparatus. The rollers in each pair have respective axes of rotation substantially parallel to each other. One pair of rollers is grooved or otherwise roughened or provided with welded-on bars, spikes or the like for gripping the surface of the timber being debarked, and for compressing the timber and bark such that the bark remains as a tube of enlarged section around the body of the tree. A second pair of rollers, including one or more knife blades, is provided downstream of the first pair of rollers, the second pair of rollers being arranged with their axes of rotation substantially perpendicular to the first pair of rollers. In another embodiment according to Wingate-Hill et al., a total of six rollers arranged in three pairs is provided, each pair having parallel axes of rotation substantially at 60.degree. relative to the respective axes of the rollers in each other pair. The Wingate-Hill et al. patent teaches that unless separate bark cutting means are provided, each of the six rollers will have respective blades attached to or formed on their outer surfaces. Another example of a debarking apparatus providing compression rollers, with circumferential knives on their outer surfaces to cut through loosened bark, is found in U.S. Pat. No. 5,111,860 issued on May 12, 1992 and also in the names of Wingate-Hill et al.
Some prior art devices do combine several tree processing operations, such as felling and bucking, delimbing and bucking, or felling, delimbing and bucking. Examples of prior art devices intended for various combined operations of tree felling, bucking or delimbing are found in U.S. Pat. No. 3,981,336 issued on Sep. 21, 1976 in the name of Levesque, Soviet Patent No. 946,458 issued on Jul. 30, 1982 in the names of Samodov et al., and International Application No. PCT/SE88/00338 published on Dec. 29, 1988, and identifying Westlund as the inventor thereof. The Levesque device comprises a harvester head having a cutting mechanism consisting of a pair of shear-like cutting edges and delimbing knives mounted to a support member. The head can be positioned vertically by a boom against a tree to be severed and then rotated into a horizontal position for the delimbing and further severing of the tree into bolts. The Soviet device mentioned above consists of a jib mounted onto a turnable, the jib providing drive rollers for translating a tree trunk through branch stripping blades. A saw attachment for felling trees may also be provided at the terminal end of the jib. As for the Westlund device, it consists of a delimbing tool having knives and a gripper which are moveable relative to one another in the axial direction of a trunk located in the gripper, such as to delimb the trunk as it is translated. A pivotable saw attachment is provided for felling and bucking of timber. None of these combined processing devices provides integrated means for debarking the processed timber.
An example of a prior art device which is intended for the combined functions tree felling and bucking is found in International Application No. PCT/SE90/00042 published on Jul. 26, 1990 and identifying Keller as the inventor thereof. The harvester according to Keller provides for two pairs of grapple arms, a feeding device in the form of a driving belt or driving wheel, and a cutting device having a pivotable guide bar around which a saw chain is rotatable at high speed. The grapple arms of Keller serve to seize the tree trunk and to delimb the trunk as it is longitudinally fed through the harvester by the feeding device. The Keller device does not provide for a debarking function.
Other devices providing for various combined tree processing functions are found in U.S. Pat. Nos. 4,194,542 and 5,219,010 issued respectively on Mar. 25, 1980 and Jun. 15, 1993, each in the name of Eriksson, U.S. Pat. No. 4,766,939 issued on Aug. 30, 1988 in the name of Forslund, and International Applications Nos. PCT/FI92/00027 and PCT/FI92/00227 published respectively on Sep. 3, 1992 and Mar. 4, 1993, each in the name of Moisio. The Eriksson patents disclose tree processing devices which include cooperating grabbing arms or delimbing members, drive rollers to feed the tree through the devices and a pivotable severing device to cut the tree. The first-mentioned Eriksson patent provides a device wherein the drive rollers are arranged on the grabbing arms in order to follow the grabbing arms towards and away from a tree. The Forslund device comprises cooperating jaw arms, feeding units for the trunk and delimbing tools moveable with the feeding units in a common plane. The Moisio devices have cooperating grapple arms, drive rollers for the trunk and articulating delimbing cutters. None of the foregoing devices provides for the capability to debark a tree being processed.
Yet other devices providing for various combined tree processing functions are found in International Application No. PCT/FI90/00147 published on Dec. 13, 1990 in the name of Ketonen, and Australian Patent No. 534,473 issued on Feb. 2, 1984 in the names of Barnett et al. The Ketonen apparatus consists of a frame, two feed tracks disposed opposite one another for translating a tree, front and rear stripping blades for delimbing, and a pivotable saw for cutting bolts to length. The Australian patent to Barnett et al. discloses a head member for tree processing which includes delimbing means, a clasping arrangement of arm members and a pair of shear knives for felling of a tree. As the head member according to Barnett et al. is caused to gravitate down a tree to its base, the momentum of the head member during the downward movement is such as to cause delimbing of the tree. The same patent also teaches that the clasping arrangement of the arm members provides for removal of at least some of the bark from the tree during its delimbing.
Many workheads of these known types are typically adapted for use with machines having a boom or beam to which the workhead is securable. Generally, workheads which are used in tree felling and processing operations are secured to a boom through an uncoupled grapple or swinging link, known in the art as a dangle connection. For instance, Canadian Patent No. 1,083,016, issued on Aug. 5, 1980 in the name of Hagan, teaches a delimbing and loading head which is articulated on the end of an arm by means of a universal joint. The joint is connected to the head at approximately its center of gravity so that it can swivel freely on two axes and automatically remain in a substantially horizontal position throughout delimbing and loading operations. Such prior art links provide for limited control of the processing head during a felling operation. Other prior art links, while providing for enhanced control of the workhead, may not achieve an appropriate range of motion for the workhead in all required directions of movement. Yet other prior art connections do not provide for ready maintenance access to electrical or hydraulic control lines, or may not be configured in a compact design.
It is therefore an object of the present invention to provide a timber processing workhead which is intended to alleviate or overcome one or more of the aforementioned disadvantages or problems associated with known timber processing workheads.
It is another object of the present invention to provide a versatile processing workhead which may serve in a plurality of timber processing functions, such as felling, delimbing, debarking, bucking, carriage and loading of trees.
It is a further object in another aspect of the present invention to provide a feed roller for use in a feed roller assembly of a timber processing workhead, which feed roller is also suited for compression debarking of felled timber.
It is a further object in another aspect of the present invention to provide a rotatable and pivotable coupled wrist connection between a processing workhead and a beam or boom to which it is connected, which is intended to provide an appropriate range of motion and a sufficient degree of control for the workhead operator involved in various timber processing activities.
It is a yet further object of the present invention to provide the rotatable and pivotable coupled wrist connection of the kind mentioned above, wherein the connection is associated with a fluid delivery manifold that is configured in a relatively compact design, and which is intended to provide for a sufficient degree of access to electrical and hydraulic control lines for maintenance purposes.